The present invention relates to a flow-through fluid filter medium product and a method of forming and assembling the same and more particularly to a unique and novel air filter blended pleated filter medium which is sufficiently stiff to incorporate self-supporting pleats, a novel filter frame optionally usable therewith for treating high velocity fluid streams and a unique method for producing the inventive product.
Blends of fiber materials for use as fluid filter media have been generally known in the fluid filtration art. For example, it has been known to blend an inexpensive cotton, shoddy material with polyester fibers to form a filter medium. In pleating such blended filter medium, the soft characteristics of the material has required the use of stream interfering back-up materials which have been comparatively expensive in manufacture and assembly and which have added to fluid stream resistance More recently, pleated blended filter media have been employed with comparatively high stiffness ratings in order to avoid the undesirable use of back-up materials. These more recently employed blended materials have been resin bonded and/or needle punched and often have been accompanied by an environmentally undesirable off-gas. Such undesirable off-gas arises mainly from the resin, which is generally used in bonding to obtain the comparatively high stiffness rating--usually with Gurley stiffness values in excess of four hundred (400) milligrams Gurley units are assigned to represent the force required to bend material, such as paper, as calculated by an established equation. The details of Gurley units are explained in a 1994 TAPPI bulletin T543 om-94. This TAPPI method has been adopted and endorsed by the Tag and Label Manufacturers, Inc. (TLMI) and a copy of the TAPPI bulletin is submitted herewith along with copies of U.S. Pat. No. 5,643,653 issued to H. L. Griesbach, III et al on Jul. 1, 1997, which describes a shaped non-woven fabric bonded without compression by an adhesive polymeric component. A number of other patents have issued on arrangements for self-supporting filters, attention being directed to U.S. Pat. No. 5,038,775, issued to J. Maruscak et al on Aug. 13, 19991; U.S. Pat. No. 5,630,856, issued to J. R. Pfeiffer on May 20, 1997 and U.S. Pat. No. 5,800,585 issued to Kyung-Ju Choi on Sep. 1, 1998, each of which teaches the utilization of a back-up serim or netting for filter medium stiffness. Attention also is directed to U.S. Pat. No. 5,597,645, issued to R. D. Pike et at on Jan. 28, 1997, U.S. Pat. No. 5,709,735, issued to D. G. Midkiff on Jan. 20, 1998; and, U.S. Pat. No. 5,855,784, issued to R. D. Pike et al on Jan. 5, 1999, each of which teaches the use of blended fibers to obtain a filter medium of high stiffness. Further, attention is directed to U.S. patent applications Ser. No. 091176,665, filed Oct. 21, 1998 now U.S. Pat. No. 6,159,318, issued Dec. 12, 2000, and Ser. No. 09/277,795, filed Mar. 27, 1999, now U.S. Pat. No. 6,165,242, issued Dec. 26, 2000, inventor Kyung-Ju Choi, both disclosing certain of the method steps incorporated with the novel method steps herein. Finally, attention is directed to above Bulletin T543 om-94 on "Bending Resistance of Paper (Gurley-type tester)", endorsed by the Tag and Label Manufacturers Institute, Inc. (TLMI).
In accordance with the present invention, a straight-forward and economical pleated filter medium product and method of making the same is provided which can be readily and inexpensively manufactured and assembled in a unique and novel manner to produce with a minimum of parts and a minimum of steps the inventive pleated filter medium product disclosed herein without the use of undesirable off-gas resins and generally without the past need of costly, resistance forming back-up materials for filtering fluid streams at conventional fluid velocities. The present invention further provides a novel filter frame which optionally can be employed with the unique self-supporting pleated product to enhance pleated filter medium support in the treatment of high velocity fluid streams without wear and tear at the pleated filter medium crests. In addition, the present invention not only recognizes and avoids the use of undesirable off-gas emitting resins in producing the novel product described herein, but provides a unique scoring and controlled heating step at preselected heating temperatures to enhance pleating without the usual synthetic filter material elastic recovery or spring-back of past pleating operations and without the use of past organic solvents and their concomitant undesirable features occasioned by curing with environmentally undesirable off-gas emissions.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure herein.